Monday, June 9 - Plenary Session

Name:  Trent Dupuy

Affiliation:  University of Texas at Austin

Title:  Testing Models of Substellar Evolution with Dynamical Masses

Evolutionary models of stars at the bottom of the main sequence and into the substellar regime are widely used, but many of their basic predictions remain essentially untested by direct measurement. We present a large sample of high precision dynamical masses for very low-mass stars and brown dwarfs via binary orbit monitoring with HST and Keck laser guide star adaptive optics. Our results more than double the number of visual binaries with dynamical masses and represents an order of magnitude increase in the sample since the beginning of our program 9 years ago. This sample of 26 binaries is now sufficiently populous to begin breaking down objects as a function of spectral type and determining the typical mass of a mid-L or early-T dwarf, for example. We also derive precise system ages from substellar evolutionary models by combining our masses with component luminosities determined from our resolved multi-band photometry. This ensemble of brown dwarf "clocks" provides a quantitative and unique record of the star formation history of low-mass objects in the solar neighborhood. In the rare cases where our brown dwarf binaries are companions to solar-type stars, we find that the substellar clocks disagree with stellar age--activity--rotation relations. We speculate that updating substellar evolutionary models to account for patchy clouds/weather could resolve this discrepancy by making brown dwarfs systematically more luminous at a given mass and age.